Ability damage boosts

[Dr Brad]

This is an interesting list:

There are many miscellaneous items and situations that can boost your ability damage. All of them work on bleeds except for Void Knight equipment and the slayer helmet and equivalents.
â—¾Black mask, Focus sight, Hexcrest, Full slayer helmet and Slayer helmet boost your ability damage by 12.5% when on a Slayer task.
â—¾Salve amulet and Salve amulet (e) boosts your ability damage by 15% and 20% respectively against undead creatures.
◾Stone of Jas boosts ability damage from 3–6% within a certain range of the ritual site.
â—¾Ferocious ring boosts ability damage by 4% when on a task in Kuradal's Dungeon.
â—¾Fremennik sea boots 4 boosts ability damage by 5% when worn while fighting any of the Dagannoth Kings.
â—¾Balmung boosts ability damage by 12% against Dagannoths.
â—¾Bane ammunition increases ability damage by 25% against appropriate monsters.
â—¾TokKul-Zo increases ability damage by 10% against TzHaar creatures.
â—¾Keris increases damage by 33% against Kalphites, and occasionally increases it by 200%.
â—¾Brine sabre and Brackish blade increase damage by 40% against 'rum'-pumped crabs.
â—¾Silverlight and Darklight double ability damage against demons.
â—¾Using the portal to the King Black Dragon in the Lava Maze increases ability damage by 10%.
â—¾Ancient Magicks increase damage by 100% against Muspahs.

Source: http://runescape.wikia.com/wiki/Ability_damage